1. Technical Field
The present invention pertains to an improvement in a conveyor system for a rotary stretch wrapping apparatus for quick and efficiently providing a continuous wrap about a product. The packaging of products to be shipped in a wrapped stretch plastic film is becoming increasingly popular, stretch wrapping offers several advantages over the use of boxes, craft paper and other conventional packaging means. In particular, stretch wrapping provides a durable, water resistant, and inexpensive covering for the product. Moreover, a product may be wrapped with great speed and thereby increase the resultant through output.
One known stretch wrapping apparatus is disclosed in U.S. Pat. No. 4,317,322 to Lancaster et al entitled ROTATABLE FILM WRAPPING APPARATUS WITH WRAP CARRYING MECHANISM. Although such a machine will provide a continuous wrap of plastic film about a product, the machine is comprised of complex, inefficient, and unbalanced components. More specifically, the Lancaster patent '322 discloses a complex conveyor system for passing the product through the wrapping machine and an off balance rotary structure adapted to circumscribe the product.
In a rotary stretch wrapping machine, the plastic film is tightly wrapped about the product and the conveyor upon which it rests. An ordinary conveyor is therefore useless since engagement of the film with the return path fights against the forward moving product. To overcome this problem, Lancaster has developed a complex conveyor system comprised of superimposed belts and an array of pulleys. However, fabrication of such a system involves high manufacturing and maintenance costs.
In a rotary stretch wrapping operation, the wrapping mechanism is spun about the product by a rotary support structure. In Lancaster '322, the rolls of film are mounted in a cantilevered manner to a circular rotary structure which is rotatably driven to effect wrapping of the product. These rolls, however, are frequently quite heavy and therefore engender large moment forces in the rotary structure as it is rotated about the product. These forces create a substantial imbalance in the structure which not only will hasten bearing wear, but also may pose a safety hazard.
This improvement to a conveyor system for a rotary film wrapping apparatus is directed primarily to the belt construction which is used in the conveyor system, see for example applicant's own U.S. Pat. Nos. 4,979,358, 5,027,579, 3,738,478, 2,962,152, 4,720,005, 3,628,651 and 3,978,979.
In applicant's own U.S. Pat. Nos. ending in 358 and 579 multiple independent lugs are shown formed of resilient resin material are reinforced composite resin construction which are positioned in spaced side to side longitudinal alignment and secured to a link chain forming the multiple lug conveyor belt configuration.
In U.S. Pat. No. 3,738,478 a conveyor chain is disclosed in which a plurality of independent supporting plates are attached to a drive chain element.
In U.S. Pat. No. 2,962,152 a conveyor track support structure is shown in which a pair of spaced parallel endless chain conveyors are positioned so that they form a multiple side by side conveyor belt configuration within a guide track.
In U.S. Pat. No. 4,720,005 a material conveyor and distribution system is disclosed in which a pair of endless conveyor belts are positioned in an angular abutting relationship to form a V-shaped trough conveyor surface. A portion of the belt is unsupported so that it forms an opening or discharge area along the conveyor surface.
In U.S. Pat. No. 3,268,651 a device for tilting advancing containers is disclosed which utilizes a pair of spaced angularly inclined conveyor belts which form a product engagement path between opposing belt surfaces for tipping the product as it engages the belt area.
Finally, in U.S. Pat. No. 3,978,979 an apparatus for arranging, separating and positioning of items to be conveyed is disclosed which is characterized by two spaced parallel movable endless conveyor elements which provide for support and transfer of uniquely shaped products therebetween by engagement of the products on the belt's edge or oppositely disposed perimeter edge surfaces.